[Collagenous colitis and chronic diarrhea]

A 68-year-old woman presented with a 4-month history of watery diarrhoea and weight loss. Radiological, analytical, endoscopic studies and intestinal biopsy were all normal. Biopsy specimens of the colonic mucosa showed the pathological features of collagenous colitis. The patient initially received mesalazine, 2 g/day, without clinical improvement; symptoms resolved following therapy with prednisone, 30 mg daily. After 2 months of prednisone therapy the diarrhea and weight loss resolved. A second colonoscopy performed 13 month after the original procedure revealed persistence of the histologic features of collagenous colitis. The diagnostic importance of total colonoscopy with multiple biopsies in a normal-appearing colon in patients with unexplained chronic watery diarrhea is stressed. Biopsies taken only from the rectum cannot exclude the diagnosis. Collagenous colitis should be considered in the differential diagnosis of chronic diarrhoea.